1. Field of the Invention
The present invention relates to constant current sources. More specifically, the present invention is directed to a stabilized constant current source using floated inertial instrument technology.
2. Description of the Prior Art
Presently precise constant current sources are based on a precision voltage reference. The zener diode, a semiconductor device, is the most commonly used precision voltage reference. The zener diode may be connected in a circuit which uses a precision resistor in series with a load to measure the current through the load. The voltage drop across the precision resistor is fed back to the negative input of an operational amplifier connected to function as an integrator. The zener diode drives the positive input of the operational amplifier. The constant current through the load is then controlled by the zener diode voltage. Such a circuit is used to provide most accuracy requirements for constant current sources since the circuit exhibits very good voltage stability and turn-on repeatability. However, in certain applications, such as ballistic missiles, there are stringent nuclear hardness requirements. Under exposure to nuclear radiation, the accuracy of the zener diode decays significantly.
Floated inertial instruments are well-known in the art as described in the publication, "Gyroscopic Theory, Design and Instrumentation" by Wrigley, Hollister and Denhard, published by the M.I.T. Press in 1969. The inertial instruments use a floated cylinder with electromagnetic suspensions that allow freedom of rotation of the cylinder. A signal generator is used with the floated cylinder in the form of a rotational transducer for detecting the motion of the cylinder and producing a representative output signal. In order to produce a stabilized constant current reference source, it would be desirable to combine the flotation technology used in modern inertial navigational instruments with a current control servo system to provide equivalent accuracy of a zener system and the capability of a rapid recovery from a nuclear event.